Vehicular repeaters are known. In FIG. 1, a vehicular repeater system operates to allow a portable (10) to communicate via a vehicular repeater (12) with a base (or base repeater) (14). This arrangement operates to increase the "talk-back" range of the portable (10) by relying upon the higher transmitter power of the vehicular repeater (12). However, a common problem with early vehicular repeater systems occurred when two or more portable units were operated in the same geographic location This situation occurs quite frequently (i.e., in most fire and police situations). The problem stems from the fact that each portable generally operates on the same frequency. Thus, each vehicular repeater would attempt to repeat all of the messages simultaneously, rendering the portable-to-base messages unintelligible.
To solve this simultaneous transmission problem, a transmission priority scheme was developed. According to the transmission priority arrangement, only one of the vehicular repeaters in a certain geographic area had priority to transmit, and assumed responsibility for repeating the messages from all of the portable units to the base station.
In FIG. 2, such a priority transmission arrangement is illustrated in flow diagram form. In step 200, the vehicular repeater is activated by any suitable automatic or manual means. In decision 202, the vehicular repeater determines whether there is any "traffic" currently on-the-air between any portable or mobile units. If so, the routine proceeds to decision 208. However, if the determination of decision 202 is that there is currently no traffic, the routine proceeds to step 204 where the vehicular repeater transmits a tone (or code) on the channel. Following this, the vehicular repeater decrements a delay counter (step 206). Typically, each vehicular repeater has a delay counter, the purpose of which is to delay repeating a message from a portable unit to the base for a predetermined amount of time (typically 400 ms.). A delay state of "zero" is the priority state, which indicates no time delay between reception of a message from a portable unit, and transmission of the repeated message to the base unit. Generally, each vehicular repeater has its delay counter initialized to a delay state of one so that no repeater is appointed apriori to the priority state. Accordingly, upon being activated (step 200) the vehicular repeater decrements its delay counter (206) and assumes the priority state if no other transmission is present.
In decision 208, the vehicular repeater determines whether or not it has received another tone (or code) on the channel. This would be the case if a later arriving unit had been activated. When a vehicular repeater receives the tone (or code) on the channel, the delay counter is incremented in step 210. Thus, a vehicular repeater operating in the priority state, relinquishes the priority state (by incrementing its delay counter), while later arriving units assume the priority state (by decrementing its delay counter). Note, however, that according to decision 202, a later arriving unit that detects traffic on the channel will not transmit the tone (or code) and decrement its delay counter. Therefore, the later arriving unit does not in all cases become the priority unit.
Decision 212 determines whether a portable in the area has transmitted a message to be repeated to the base unit. If the determination of decision 212 is that there are no messages to be repeated, the routine proceeds to decision 208 where the vehicular repeater operates to either receive a message or receive a tone, which adjusts which particular vehicular repeater operates in the priority state. If however, decision 212 determines that there is a message to repeat, each vehicular repeater will begin a count-down timer (step 214) the duration of which depends upon the state of its priority counter. Thus, the repeater in the priority state would have a count-down timer of zero, repeaters in priority state one would wait one delay interval (typically 400 ms), repeaters in delay state two would wait two delay intervals, and so on. Decision 216 determines whether another vehicular repeater has transmitted (repeated) the message. Generally, an affirmative determination would result from decision 216 for all repeaters having a delay state higher than the priority state. That is, the priority repeater having a zero delay interval would repeat immediately and all other repeaters delaying their transmission would return to decision 212 upon detection of the transmission. If however, the priority repeater has left the area (or become disabled), the routine proceeds from decision 216 to decision 218, which determines whether the count down timer has completely counted down. If not, control returns to step 214, so that a loop is formed to either continue the count-down process, or to exit via decision 216. If the determination of decision 218 is that the timer has completely counted down, the routine proceeds to step 220, which decrements the delay counter so that another repeater will either assume the priority state, or move closer to assuming the priority state (i.e., such as moving from delay state 2 to delay state 1). In step 222, the repeater transmits the message and returns control to decision 212. In this way, another repeater may assume the priority state.
While the prioritization system described in conjunction with FIG. 2 is suitable for vehicular repeaters such as automobiles and trucks, such a prioritization scheme is unsuitable for other vehicles such as motorcycles, which have a smaller battery having a shorter battery life. Thus, should a motorcycle unit assume the priority state, it would be responsible for repeating all messages from all portables and may rapidly have its battery supply exhausted. Of course, another vehicular repeater may assume the priority state so that communications are maintained, however, at the conclusion of the emergency (or situation) the officer assigned to the motorcycle would discover that his motorcycle is inoperative Therefore, a need exists to be able to add a second level of vehicular repeaters that have specialized requirements or limitations compared to other (i.e., the primary) vehicular repeaters.
Accordingly, it is an object of the present invention to provide an improved vehicular repeater system.
It is a further object of the present invention to provide a vehicular repeater system having two levels of transmission responsibility.
It is another object of the present invention to provide transmission priority within each of the two transmission levels of the vehicular repeater system of the present invention.